1. Field of the Invention
The present invention is directed to contact lenses and more particularly to lenses made of synthetic polymer material having specific characteristic capabilities. These include the ability to begin change while in use and, in a predetermined period of time, the ability to have the change translated into a recognizable signal to dispose of or otherwise replace the lenses.
2. Prior Art Statement
Current contact lenses are sophisticated despite their small size and apparent simplicity. Most lenses have been designed for long term intimate contact with living tissue (namely, the cornea), and, as a result, the requirements for edge and surface quality are extremely high. The surface quality of a lens may be compromised by deposits of foreign matter; by scratches from handling; by cracks from environmental stress; by embedded particles, such as dust specks; by colonies of microorganisms and their residuals; and by combinations of these, as well as other detrimental factors. Contact lenses are generally maintained by cleaning and disinfection procedures which help to maintain their quality but which may also cause another kind of deterioration. The current lenses have to be cleaned, disinfected and maintained by the individual user. The errors or neglect in the cleaning procedures not only deteriorate the lens quality, but may also create a direct hazard to the eye. The cumulative effect of the time induced deterioration and deviations from optimum cleaning procedures are increased health risk and decreased benefit to the user.
Therefore, contact lenses can be functionally better and safer when used as disposable items to be discarded after performing their function for an optimum period of time. In other words, for the good of the user's health, as well as simplicity of use, total elimination of cleaning procedures by the user is preferred. Motivated by both health considerations and convenience considerations for their customers, manufacturers have developed and marketed certain types of contact lenses as disposable goods.
One problem with the current disposable lenses is that they are functionally indistinguishable from much more expensive contact lenses sold as permanent or "use until destroyed" devices. The current coexistence of two very differently priced versions of what appears to the user to be the same device poses certain risks of error or misuse. This would be not only detrimental to trade, but ultimately could increase the risk to the user.
To avoid this confusion and risk, it is desirable that the disposable lens differ from the repeated-use lens in such a way that the former type cannot be misused as the lens for repeated or permanent use. This difference cannot be one of safety or efficacy or comfort of the lens during the initial use, or it would not be a viable product.
Instead, the present invention is directed to the use of a "self-destruct" feature, promoting the use as a disposable item and preventing or discouraging the misuse. In other words, lens properties (such as wear comfort, vision quality, appearance etc.) should change after a certain period of time to encourage the user to replace his or her lenses, without complicating the functioning of the lenses or confusing the user.
The present invention is based on this unsatisfied need and is neither taught nor suggested by the current state of the art.